Auditory outcomes after scala vestibuli array insertion are similar to those after scala tympani insertion 1 year after cochlear implantation.

PURPOSE: In cochlear implantation, a scala vestibuli (SV) insertion of an electrode array is a rare occurrence and is reported to be linked to poor hearing outcomes. Using the same electrode array, the auditory performance of patients with a complete SV location was compared with that of patients having a complete scala tympani (ST) location 1 year after implantation. METHODS: Thirty-three patients were included in this retrospective case-control study (SV, n = 12; ST, n = 21). The matching criteria were electrode array type, age at implantation, and duration of severe or profound deafness. The array location was analyzed using 3D reconstruction of postoperative CT scans. Postoperative audiological evaluation of the implanted ear was performed using pure-tone audiometry, speech recognition of monosyllabic words in quiet, and words and sentences in noise. RESULTS: On the preoperative CT scan, six patients in the SV group presented with both round window (RW) and ST ossification, three with RW ossification alone, and three with no RW ossification. Auditory performance did not differ between SV and ST groups 1 year after cochlear implantation. Speech recognition of words was 49 ± 7.6% and 56 ± 5.0% in quiet and 75 ± 9.5% and 66 ± 6.0% in noise in SV and ST groups, respectively. CONCLUSION: ST insertion is the gold standard that allows the three cochlear scalae to preserve scalar cochlear integrity. However, 1 year after implantation, a planned or unexpected SV insertion is not detrimental to hearing outcomes, providing similar auditory performance in quiet and noise to ST insertion.

Incomplete Partition Type II Cochlear Malformations: Delineating the Three-Dimensional Structure from Digitized Human Histopathological Specimens.

HYPOTHESIS: There are clinically relevant differences in scalae anatomy and spiral ganglion neuron (SGN) quantity between incomplete partition type II (IP-II) and normal cochleae. BACKGROUND: IP-II is a commonly implanted cochlear malformation. Detailed knowledge of intracochlear three-dimensional (3D) morphology may assist with cochlear implant (CI) electrode selection/design and enable optimization of audiologic programming based on SGN maps. METHODS: IP-II (n = 11) human temporal bone histological specimens were identified from the National Institute on Deafness and Other Communication Disorders National Temporal Bone Registry and digitized. The cochlear duct, scalae, and surgically relevant anatomy were reconstructed in 3D. A machine learning algorithm was applied to map the location and number of SGNs. RESULTS: 3D scalae morphology of the basal turn was normal. Scala tympani (ST) remained isolated for 540 degrees before fusing with scala vestibuli. Mean ST volume reduced below 1 mm 2 after the first 340 degrees. Scala media was a distinct endolymphatic compartment throughout; mean ± standard deviation cochlear duct length was 28 ± 3 mm. SGNs were reduced compared with age-matched norms (mean, 48%; range, 5-90%). In some cases, SGNs failed to ascend Rosenthal's canal, remaining in an abnormal basalward modiolar location. Two forms of IP-II were seen: type A and type B. A majority (98-100%) of SGNs were located in the basal modiolus in type B IP-II, compared with 76 to 85% in type A. CONCLUSION: Hallmark features of IP-II cochleae include the following: 1) fusion of the ST and scala vestibuli at a mean of 540 degrees, 2) highly variable and overall reduced SGN quantity compared with normative controls, and 3) abnormal SGN distribution with cell bodies failing to ascend Rosenthal's canal.

Dynamic Behavior and Insertional Forces of a Precurved Electrode Using the Pull-Back Technique in a Fresh Microdissected Cochlea.

HYPOTHESIS: This study evaluated the utility of the pull-back technique in improving perimodiolar positioning of a precurved cochlear implant (CI) electrode array (EA) with simultaneous insertion force profile measurement and direct observation of dynamic EA behavior. BACKGROUND: Precurved EAs with perimodiolar positioning have improved outcomes compared with straight EAs because of lowered charge requirements for stimulation and decreased spread of excitation. The safety and efficacy of the pull-back technique in further improving perimodiolar positioning and its associated force profile have not been adequately demonstrated. METHODS: The bone overlying the scala vestibuli was removed in 15 fresh cadaveric temporal bones, leaving the scala tympani unviolated. Robotic insertions of EAs were performed with simultaneous force measurement and video recording. Force profiles were obtained during standard insertion, overinsertion, and pull-back. Postinsertion CT scans were obtained during each of the three conditions, enabling automatic segmentation and calculation of angular insertion depth, mean perimodiolar distance ( Mavg ), and cochlear duct length. RESULTS: Overinsertion did not result in significantly higher peak forces than standard insertion (mean [SD], 0.18 [0.06] and 0.14 [0.08] N; p = 0.18). Six temporal bones (40%) demonstrated visibly improved perimodiolar positioning after the protocol, whereas none worsened. Mavg significantly improved after the pull-back technique compared with standard insertion (mean [SD], 0.34 [0.07] and 0.41 [0.10] mm; p < 0.01). CONCLUSIONS: The pull-back technique was not associated with significantly higher insertional forces compared with standard insertion. This technique was associated with significant improvement in perimodiolar positioning, both visually and quantitatively, independent of cochlear size.

Real-time measurement of stapes motion and intracochlear pressure during blast exposure.

Blast-induced auditory injury is primarily caused by exposure to an overwhelming amount of energy transmitted into the external auditory canal, the middle ear, and then the cochlea. Quantification of this energy requires real-time measurement of stapes footplate (SFP) motion and intracochlear pressure in the scala vestibuli (Psv). To date, SFP and Psv have not been measured simultaneously during blast exposure, but a dual-laser experimental approach for detecting the movement of the SFP was reported by Jiang et al. (2021). In this study, we have incorporated the measurement of Psv with SFP motion and developed a novel approach to quantitatively measure the energy flux entering the cochlea during blast exposure. Five fresh human cadaveric temporal bones (TBs) were used in this study. A mastoidectomy and facial recess approach were performed to identify the SFP, followed by a cochleostomy into the scala vestibuli (SV). The TB was mounted to the "head block", a fixture to simulate a real human skull, with two pressure sensors - one inserted into the SV (Psv) and another in the ear canal near the tympanic membrane (P1). The TB was exposed to the blast overpressure (P0) around 4 psi or 28 kPa. Two laser Doppler vibrometers (LDVs) were used to measure the movements of the SFP and TB (as a reference). The LDVs, P1, and Psv signals were triggered by P0 and recorded simultaneously. The results include peak values for Psv of 100.8 ± 51.6 kPa (mean ± SD) and for SFP displacement of 72.6 ± 56.4 µm, which are consistent with published experimental results and finite element modeling data. Most of the P0 input energy flux into the cochlea occurred within 2 ms and resulted in 10-70 µJ total energy entering the cochlea. Although the middle ear pressure gain was close to that measured under acoustic stimulus conditions, the nonlinear behavior of the middle ear was observed from the elevated cochlear input impedance. For the first time, SFP movement and intracochlear pressure Psv have been successfully measured simultaneously during blast exposure. This study provides a new methodology and experimental data for determining the energy flux entering the cochlea during a blast, which serves as an injury index for quantifying blast-induced auditory damage.

Prolonged Insertion Time Reduces Translocation Rate of a Precurved Electrode Array in Cochlear Implantation.

HYPOTHESIS: Insertion speed during cochlear implantation determines the risk of cochlear trauma. By slowing down insertion speed tactile feedback is improved. This is highly conducive to control the course of the electrode array along the cochlear contour and prevent translocation from the scala tympani to the scala vestibuli. BACKGROUND: Limiting insertion trauma is a dedicated goal in cochlear implantation to maintain the most favorable situation for electrical stimulation of the remaining stimulable neural components of the cochlea. Surgical technique is one of the potential influencers on translocation behavior of the electrode array. METHODS: The intrascalar position of 226 patients, all implanted with a precurved electrode array, aiming a mid-scalar position, was evaluated. One group (n = 113) represented implantation with an insertion time less than 25 seconds (fast insertion) and the other group (n = 113) was implanted in 25 or more seconds (slow insertion). A logistic regression analysis studied the effect of insertion speed on insertion trauma, controlled for surgical approach, cochlear size, and angular insertion depth. Furthermore, the effect of translocation on speech performance was evaluated using a linear mixed model. RESULTS: The translocation rate within the fast and slow insertion groups were respectively 27 and 10%. A logistic regression analysis showed that the odds of dislocation increases by 2.527 times with a fast insertion, controlled for surgical approach, cochlear size, and angular insertion depth (95% CI = 1.135, 5.625). We failed to find a difference in speech recognition between patients with and without translocated electrode arrays. CONCLUSION: Slowing down insertion speed till 25 seconds or longer reduces the incidence of translocation.

Scala vestibuli cochlear implant supported by 3D modeling of the inner ear.

Patients with scala tympani (ST) ossification present a distinct surgical challenge. Three-dimensional (3D) segmentation of the inner ear offers accurate identification of ossification and surgical planning of the cochleostomy to access the scala vestibuli. The scala vestibuli placement of cochlear implantation electrode is an alternate solution in these patients and is well supported by the literature.The present report describes a case of cochlear implantation in the scala vestibuli assisted by 3D segmentation of the cochlea for a patient with ossification in the ST and reviews the relevant literature. Clinical presentation of a 45-year-old Austrian female who was referred with a history of sudden sensorineural hearing loss 2 years ago in the right ear, confirmed by pure tone audiometry (PTA) and acoustically evoked auditory brainstem response (ABR). 3D segmentation of the inner ear identified the extent of ossification in the ST and assisted in the surgical planning of cochleostomy drilling anterior-superior to the round window to access the scala vestibuli for the electrode placement. Postoperative computed tomography (CT) to confirm the electrode placement in the scala vestibuli and PTA was performed to assess the hearing threshold following the cochlear implantation. Postoperative CT confirmed the full insertion of a flexible electrode. The hearing threshold measured by PTA was ≤ 40 dB across all frequencies tested. Review of the literature identified a total of 13 published reports on cochlear implantation electrode placement in scala vestibuli in cases with ossification in the ST.

Middle Ear Actuator Performance Determined From Intracochlear Pressure Measurements in a Single Cochlear Scala.

HYPOTHESIS: Intracochlear pressure measurements in one cochlear scala are sufficient as reference to determine the output of an active middle ear implant (AMEI) in terms of "equivalent sound pressure level" (eqSPL). BACKGROUND: The performance of AMEIs is commonly calculated from stapes velocities or intracochlear pressure differences (PDiff). However, there are scenarios where measuring stapes velocities or PDiff may not be feasible, for example when access to the stapes or one of the scalae is impractical. METHODS: We reanalyzed data from a previous study of our group that investigated the performance of an AMEI coupled to the incus in 10 human temporal bones. We calculated eqSPL based on stapes velocities according to the ASTM standard F2504-05 and based on intracochlear pressures in scala vestibuli, scala tympani, and PDiff. RESULTS: The AMEI produced eqSPL of ∼100 to 120 dB at 1 Vrms. No significant differences were found between using intracochlear pressures in scala vestibuli, scala tympani, or PDiff as a reference. The actuator performance calculated from stapes displacements predicted slightly higher eqSPLs at frequencies above 1000 Hz, but these differences were not statistically significant. CONCLUSION: Our findings show that pressure measurements in one scala can be sufficient to evaluate the performance of an AMEI coupled to the incus. The method may be extended to other stimulation modalities of the middle ear or cochlea when access to the stapes or one of the scalae is not possible.

Into and out of the cochlea: A re-implantation saga.

Introduction: In patients with normal inner ear architecture at imaging and who received a prior cochlear implant (CI) without difficulty, the expectation is that replacing a failed CI should be straightforward. Here, we present a patient in whom an unusual complication (to our knowledge, not reported) was encountered. Methods: Review of audiological and medical and surgical records and imaging data. Results: Re-implantation went well except no electrically elicited compound action potential could be elicited via any electrode. The replacement CI did not provide any auditory perception. CT showed the electrode array to enter the cochlea with three electrodes, but all other electrodes extended toward the Eustachian tube. Subsequent re-implantation into the scala vestibuli yielded excellent performance with the CI. Conclusion: Mechanical forces, such as from a CI array, can erode the hardest bone over time. This possibility should be a consideration in patients who are undergoing CI device replacement.

Evaluation After Cochlear Implant Surgery : Correlation of Clinical Outcome and Imaging Findings using Flat-detector CT.

PURPOSE: Assessment of the cochlear implant (CI) electrode array position using flat-detector computed tomography (FDCT) to test dependence of postoperative outcome on intracochlear electrode position. METHODS: A total of 102 patients implanted with 107 CIs underwent FDCT. Electrode position was rated as 1) scala tympani, 2) scala vestibuli, 3) scalar dislocation and 4) no deconvolution. Two independent neuroradiologists rated all image data sets twice and the scalar position was verified by a third neuroradiologist. Presurgical and postsurgical speech audiometry by the Freiburg monosyllabic test was used to evaluate auditory outcome after 6 months of speech rehabilitation. RESULTS: Electrode array position was assessed by FDCT in 107 CIs. Of the electrodes 60 were detected in the scala tympani, 21 in the scala vestibuli, 24 electrode arrays showed scalar dislocation and 2 electrodes were not placed in an intracochlear position. There was no significant difference in rehabilitation outcomes between scala tympani and scala vestibuli inserted patients. Rehabilitation was also possible in patients with dislocated electrodes. CONCLUSION: The use of FDCT is a reliable diagnostic method to determine the position of the electrode array. In our study cohort, the electrode position had no significant impact on postoperative outcome except for non-deconvoluted electrode arrays.

Deep Volumetric Segmentation of Murine Cochlear Compartments from Micro-Computed Tomography Images.

Local drug delivery to the inner ear via micropump implants has the potential to be much more effective than oral drug delivery for treating patients with sensorineural hearing loss and to protect hearing from ototoxic insult due to noise exposure or cancer treatments. Designing micropumps to deliver appropriate concentrations of drugs to the necessary cochlear compartments is of paramount importance; however, directly measuring local drug concentrations over time throughout the cochlea is not possible. Recent approaches for indirectly quantifying local drug concentrations in animal models capture a series of magnetic resonance (MR) or micro computed tomography (µCT) images before and after infusion of a contrast agent into the cochlea. These approaches require accurately segmenting important cochlear components (scala tympani (ST), scala media (SM) and scala vestibuli (SV)) in each scan and ensuring that they are registered longitudinally across scans. In this paper, we focus on segmenting cochlear compartments from µCT volumes using V-Net, a convolutional neural network (CNN) architecture for 3-D segmentation. We show that by modifying the V-Net architecture to decrease the numbers of encoder and decoder blocks and to use dilated convolutions enables extracting local estimates of drug concentration that are comparable to those extracted using atlas-based segmentation (3.37%, 4.81%, and 19.65% average relative error in ST, SM, and SV), but in a fraction of the time. We also test the feasibility of training our network on a larger MRI dataset, and then using transfer learning to perform segmentation on a smaller number of µCT volumes, which would enable this technique to be used in the future to characterize drug delivery in the cochlea of larger mammals.

Superior Canal Dehiscence Similarly Affects Cochlear Pressures in Temporal Bones and Audiograms in Patients.

OBJECTIVES: The diagnosis of superior canal dehiscence (SCD) is challenging and audiograms play an important role in raising clinical suspicion of SCD. The typical audiometric finding in SCD is the combination of increased air conduction (AC) thresholds and decreased bone conduction thresholds at low frequencies. However, this pattern is not always apparent in audiograms of patients with SCD, and some have hearing thresholds that are within the normal reference range despite subjective reports of hearing impairment. In this study, we used a human temporal bone model to measure the differential pressure across the cochlear partition (PDiff) before and after introduction of an SCD. PDiff estimates the cochlear input drive and provides a mechanical audiogram of the temporal bone. We measured PDiff across a wider frequency range than in previous studies and investigated whether the changes in PDiff in the temporal bone model and changes of audiometric thresholds in patients with SCD were similar, as both are thought to reflect the same physical phenomenon. DESIGN: We measured PDiff across the cochlear partition in fresh human cadaveric temporal bones before and after creating an SCD. Measurements were made for a wide frequency range (20 Hz to 10 kHz), which extends down to lower frequencies than in previous studies and audiograms. PDiff = PSV- PST is calculated from pressures measured simultaneously at the base of the cochlea in scala vestibuli (PSV) and scala tympani (PST) during sound stimulation. The change in PDiff after an SCD is created quantifies the effect of SCD on hearing. We further included an important experimental control-by patching the SCD, to confirm that PDiff was reversed back to the initial state. To provide a comparison of temporal bone data to clinical data, we analyzed AC audiograms (250 Hz to 8kHz) of patients with symptomatic unilateral SCD (radiographically confirmed). To achieve this, we used the unaffected ear to estimate the baseline hearing function for each patient, and determined the influence of SCD by referencing AC hearing thresholds of the SCD-affected ear with the unaffected contralateral ear. RESULTS: PDiff measured in temporal bones (n = 6) and AC thresholds in patients (n = 53) exhibited a similar pattern of SCD-related change. With decreasing frequency, SCD caused a progressive decrease in PDiff at low frequencies for all temporal bones and a progressive increase in AC thresholds at low frequencies. SCD decreases the cochlear input drive by approximately 6 dB per octave at frequencies below ~1 kHz for both PDiff and AC thresholds. Individual data varied in frequency and magnitude of this SCD effect, where some temporal-bone ears had noticeable effects only below 250 Hz. CONCLUSIONS: We found that with decrease in frequency the progressive decrease in low-frequency PDiff in our temporal bone experiments mirrors the progressive elevation in AC hearing thresholds observed in patients. This hypothesis remains to be tested in the clinical setting, but our findings suggest that that measuring AC thresholds at frequencies below 250 Hz would detect a larger change, thus improving audiograms as a diagnostic tool for SCD.

A Comparison of Intracochlear Pressures During Ipsilateral and Contralateral Stimulation With a Bone Conduction Implant.

OBJECTIVES: To compare contralateral to ipsilateral stimulation with percutaneous and transcutaneous bone conduction implants. BACKGROUND: Bone conduction implants (BCIs) effectively treat conductive and mixed hearing losses. In some cases, such as in single-sided deafness, the BCI is implanted contralateral to the remaining healthy ear in an attempt to restore some of the benefits provided by binaural hearing. While the benefit of contralateral stimulation has been shown in at least some patients, it is not clear what cues or mechanisms contribute to this function. Previous studies have investigated the motion of the ossicular chain, skull, and round window in response to bone vibration. Here, we extend those reports by reporting simultaneous measurements of cochlear promontory velocity and intracochlear pressures during bone conduction stimulation with two common BCI attachments, and directly compare ipsilateral to contralateral stimulation. METHODS: Fresh-frozen whole human heads were prepared bilaterally with mastoidectomies. Intracochlear pressure (PIC) in the scala vestibuli (PSV) and tympani (PST) was measured with fiber optic pressure probes concurrently with cochlear promontory velocity (VProm) via laser Doppler vibrometry during stimulation provided with a closed-field loudspeaker or a BCI. Stimuli were pure tones between 120 and 10,240 Hz, and response magnitudes and phases for PIC and VProm were measured for air and bone conducted sound presentation. RESULTS: Contralateral stimulation produced lower response magnitudes and longer delays than ipsilateral in all measures, particularly for high-frequency stimulation. Contralateral response magnitudes were lower than ipsilateral response magnitudes by up to 10 to 15 dB above ~2 kHz for a skin-penetrating abutment, which increased to 25 to 30 dB and extended to lower frequencies when applied with a transcutaneous (skin drive) attachment. CONCLUSIONS: Transcranial attenuation and delay suggest that ipsilateral stimulation will be dominant for frequencies over ~1 kHz, and that complex phase interactions will occur during bilateral or bimodal stimulation. These effects indicate a mechanism by which bilateral users could gain some bilateral advantage.

Intracochlear Electrocochleography: Influence of Scalar Position of the Cochlear Implant Electrode on Postinsertion Results.

HYPOTHESIS: Electrocochleography (ECochG) recorded during cochlear implant (CI) insertion from the apical electrode in conjunction with postinsertion ECochG can identify electrophysiologic differences that exist between groups with and without a translocation of the array from the scala tympani (ST) into the scala vestibuli (SV). BACKGROUND: Translocation of the CI electrode from ST into SV can limit performance postoperatively. ECochG markers of trauma may be able to aid in the ability to detect electrode array-induced trauma/scalar translocation intraoperatively. METHODS: Twenty-one adult CI patients were included. Subjects were postoperatively parsed into two groups based on analysis of postoperative imaging: 1) ST (n = 14) insertion; 2) SV (n = 7) insertion, indicating translocation of the electrode. The ECochG response elicited from a 500 Hz acoustic stimulus was recorded from the lead electrode during insertion when the distal electrode marker was at the round window, and was compared to the response recorded from a basal electrode (e13) after complete insertion. RESULTS: No statistically significant change in mean ECochG magnitude was found in either group between recording intervals. There was a mean loss of preoperative pure-tone average of 52% for the nontranslocation group and 94% for the translocation group. CONCLUSIONS: Intraoperative intracochlear ECochG through the CI array provides a unique opportunity to explore the impact of the CI electrode on the inner ear. Specifically, a translocation of the array from ST to SV does not seem to change the biomechanics of the cochlear region that lies basal to the area of translocation in the acute period.

Another evidence for pressure transfer mechanism in incomplete partition two anomaly via enlarged vestibular aqueduct.

A female patient with unilateral enlarged vestibular aqueduct (EVA) demonstrated scala vestibuli dilatation on that side while on the contralateral side both vestibular aqueduct and scala vestibuli were normal. This important radiological finding demonstrates that modiolar defects (hence 'cystic apex') observed in Incomplete partition-II is due to pressure transfer via EVA during embryological development. Therefore, it supports the previous histopathological ideas radiologically. Depending on the patency of EVA, variety of modiolar defects may arise.

Intracochlear pressure measurements during acoustic shock wave exposure.

INTRODUCTION: Injuries to the peripheral auditory system are among the most common results of high intensity impulsive acoustic exposure. Prior studies of high intensity sound transmission by the ossicular chain have relied upon measurements in animal models, measurements at more moderate sound levels (i.e. < 130 dB SPL), and/or measured responses to steady-state noise. Here, we directly measure intracochlear pressure in human cadaveric temporal bones, with fiber optic pressure sensors placed in scala vestibuli (SV) and tympani (ST), during exposure to shock waves with peak positive pressures between ∼7 and 83 kPa. METHODS: Eight full-cephalic human cadaver heads were exposed, face-on, to acoustic shock waves in a 45 cm diameter shock tube. Specimens were exposed to impulses with nominal peak overpressures of 7, 28, 55, & 83 kPa (171, 183, 189, & 192 dB pSPL), measured in the free field adjacent to the forehead. Specimens were prepared bilaterally by mastoidectomy and extended facial recess to expose the ossicular chain. Ear canal (EAC), middle ear, and intracochlear sound pressure levels were measured with fiber-optic pressure sensors. Surface-mounted sensors measured SPL and skull strain near the opening of each EAC and at the forehead. RESULTS: Measurements on the forehead showed incident peak pressures approximately twice that measured by adjacent free-field and EAC entrance sensors, as expected based on the sensor orientation (normal vs tangential to the shock wave propagation). At 7 kPa, EAC pressure showed gain, calculated from the frequency spectra, consistent with the ear canal resonance, and gain in the intracochlear pressures (normalized to the EAC pressure) were consistent with (though somewhat lower than) previously reported middle ear transfer functions. Responses to higher intensity impulses tended to show lower intracochlear gain relative to EAC, suggesting sound transmission efficiency along the ossicular chain is reduced at high intensities. Tympanic membrane (TM) rupture was observed following nearly every exposure 55 kPa or higher. CONCLUSIONS: Intracochlear pressures reveal lower middle-ear transfer function magnitudes (i.e. reduced gain relative to the ear canal) for high sound pressure levels, thus revealing lower than expected cochlear exposure based on extrapolation from cochlear pressures measured at more moderate sound levels. These results are consistent with lowered transmissivity of the ossicular chain at high intensities, and are consistent with our prior report measuring middle ear transfer functions in human cadaveric temporal bones with high intensity tone pips.

Comparative Impacts of Scala Vestibuli Versus Scala Tympani Cochlear Implantation on Auditory Performances and Programming Parameters in Partially Ossified Cochleae.

OBJECTIVE: To compare scala vestibuli versus scala tympani cochlear implantation in terms of postoperative auditory performances and programming parameters in patients with severe scala tympani ossification. STUDY DESIGN: Retrospective case-control study. SETTING: Tertiary referral center. PATIENTS: One hundred three pediatric and adult patients who underwent cochlear implant surgery between 2000 and 2016. Three groups were formed: a scala vestibuli group, a scala tympani with ossification group, and a scala tympani without ossification group. Patients were matched based on their age, sex, duration of deafness, and side of implantation (ratio of 1:2:2). INTERVENTIONS: Postoperative evaluation of auditory performances and programming parameters following intensive functional rehabilitation program completion. MAIN OUTCOME MEASURES: Multimedia adaptive test (MAT), hearing in noise test (HINT SNR +10 dB, HINT SNR +5 dB, and HINT SNR +0 dB), impedances, neural response telemetry thresholds (NRT), neural response imaging thresholds (NRI), comfortable levels (C-levels), and threshold levels (T-levels) were compared between groups. RESULTS: Twenty-one patients underwent scala vestibuli cochlear implantation: 19 adults and two children. Auditory performances were similar between groups, although sentence recognition in a noisy environment was slightly higher in the scala vestibuli group. Impedance values were also higher in the scala vestibuli group, but all other programming parameters were similar between groups. CONCLUSIONS: We present the largest series of patients with scala vestibuli cochlear implantation. This approach provides at least comparable auditory performances without having any deleterious effects on programming parameters. This viable and useful insertion route might be the primary surgical alternative when facing partial cochlear ossification.

Cochlear Implantation in Otosclerosis: Surgical and Auditory Outcomes With a Brief on Facial Nerve Stimulation.

OBJECTIVES: 1) To review the surgical and auditory outcomes in patients of cochlear implantation in otosclerosis. 2) To review complications and postimplantation facial nerve stimulation (FNS). 3) To compare the auditory outcomes between patients displaying cochlear ossification to the nonossified ones. STUDY DESIGN: Retrospective study. SETTING: Quaternary Otology and Skull base surgery center. SUBJECTS AND METHODS: Charts of 36 patients (38 ears) with otosclerosis undergoing cochlear implantation were reviewed from the cochlear implant database. Demographic features, operative findings, auditory outcomes, and postimplantation FNS were analyzed. Operative findings included extent of cochlear ossification, approach (posterior tympantomy/subtotal petrosectomy), electrode insertion (partial/complete, scala tympani/vestibuli), and complications. All the patients underwent implantation using straight electrodes. Auditory outcomes were assessed over a 4-year follow-up period using vowel, word, sentence, and comprehension scores. Patients were divided into two groups (with and without cochlear ossification) for comparison of auditory outcomes. RESULTS: The mean age and duration of deafness of patients was 59.72 and 28.9 years respectively. Twenty-three of 38 ears had cochlear ossification, with exclusive round window involvement in 60% of the patients, with the rest having partial or complete basal turn ossification. 36.8% ears underwent subtotal petrosectomy for cochlear ossification. One patient underwent scala vestibuli insertion and two had incomplete electrode insertion. Patients with no ossification had no intra or postoperative complications. One patient had bilateral FNS managed by alterations in programming strategy. Auditory outcomes in patients without any ossification were better than in patients with ossification, though statistically insignificant in most parameters. CONCLUSION: Cochlear implantation in otosclerosis provides good auditory outcomes, despite high incidence of cochlear ossification. Patients of FNS can be managed by alterations in programming strategy, without affecting auditory outcomes.

Semicircular Canal Pressure Changes During High-intensity Acoustic Stimulation.

HYPOTHESIS: Acoustic stimulation generates measurable sound pressure levels in the semicircular canals. BACKGROUND: High-intensity acoustic stimuli can cause hearing loss and balance disruptions. To examine the propagation of acoustic stimuli to the vestibular end-organs, we simultaneously measured fluid pressure in the cochlea and semicircular canals during both air- and bone-conducted sound presentation. METHODS: Five full-cephalic human cadaveric heads were prepared bilaterally with a mastoidectomy and extended facial recess. Vestibular pressures were measured within the superior, lateral, and posterior semicircular canals, and referenced to intracochlear pressure within the scala vestibuli with fiber-optic pressure probes. Pressures were measured concurrently with laser Doppler vibrometry measurements of stapes velocity during stimulation with both air- and bone-conduction. Stimuli were pure tones between 100 Hz and 14 kHz presented with custom closed-field loudspeakers for air-conducted sounds and via commercially available bone-anchored device for bone-conducted sounds. RESULTS: Pressures recorded in the superior, lateral, and posterior semicircular canals in response to sound stimulation were equal to or greater in magnitude than those recorded in the scala vestibuli (up to 20 dB higher). The pressure magnitudes varied across canals in a frequency-dependent manner. CONCLUSION: High sound pressure levels were recorded in the semicircular canals with sound stimulation, suggesting that similar acoustical energy is transmitted to the semicircular canals and the cochlea. Since these intralabyrinthine pressures exceed intracochlear pressure levels, our results suggest that the vestibular end-organs may also be at risk for injury during exposure to high-intensity acoustic stimuli known to cause trauma in the auditory system.

Stapes displacement and intracochlear pressure in response to very high level, low frequency sounds.

The stapes is held in the oval window by the stapedial annular ligament (SAL), which restricts total peak-to-peak displacement of the stapes. Previous studies have suggested that for moderate (<130 dB SPL) sound levels intracochlear pressure (PIC), measured at the base of the cochlea far from the basilar membrane, increases directly proportionally with stapes displacement (DStap), thus a current model of impulse noise exposure (the Auditory Hazard Assessment Algorithm for Humans, or AHAAH) predicts that peak PIC will vary linearly with DStap up to some saturation point. However, no direct tests of DStap, or of the relationship with PIC during such motion, have been performed during acoustic stimulation of the human ear. In order to examine the relationship between DStap and PIC to very high level sounds, measurements of DStap and PIC were made in cadaveric human temporal bones. Specimens were prepared by mastoidectomy and extended facial recess to expose the ossicular chain. Measurements of PIC were made in scala vestibuli (PSV) and scala tympani (PST), along with the SPL in the external auditory canal (PEAC), concurrently with laser Doppler vibrometry (LDV) measurements of stapes velocity (VStap). Stimuli were moderate (∼100 dB SPL) to very high level (up to ∼170 dB SPL), low frequency tones (20-2560 Hz). Both DStap and PSV increased proportionally with sound pressure level in the ear canal up to approximately ∼150 dB SPL, above which both DStap and PSV showed a distinct deviation from proportionality with PEAC. Both DStap and PSV approached saturation: DStap at a value exceeding 150 µm, which is substantially higher than has been reported for small mammals, while PSV showed substantial frequency dependence in the saturation point. The relationship between PSV and DStap remained constant, and cochlear input impedance did not vary across the levels tested, consistent with prior measurements at lower sound levels. These results suggest that PSV sound pressure holds constant relationship with DStap, described by the cochlear input impedance, at these, but perhaps not higher, stimulation levels. Additionally, these results indicate that the AHAAH model, which was developed using results from small animals, underestimates the sound pressure levels in the cochlea in response to high level sound stimulation, and must be revised.